Carboxamides are important compounds as a variety of chemical products such as active ingredients of medicines and pesticides, and electronic materials, and synthetic intermediates thereof (see, for example, WO2004/065374).
In WO2004/065374 is disclosed a method in which ethyl 4,5-bis(4-methoxyphenyl)-1,3-oxazole-2-carboxylate, which is a carboxylic acid ester, is allowed to react with formamide in the presence of sodium methoxide, which is a metal alkoxide, to give 4,5-bis(4-methoxyphenyl)-1,3-oxazole-2-carboxamide, which is a carboxamide, in a yield of 71.9% (see Example 2).
However, the method is not necessarily satisfactory in the yield of the carboxamide to be obtained.
Thus, new methods by which a carboxamide can be produced from a carboxylic acid ester in a high yield have been awaited.